Tubular drafting pen with improved writing point assembly

Abstract

A writing point assembly for a tubular drafting pen includes an elongated tubular shell from one end of which a tubular, capillary nib projects. A sliding weight guided in the shell axially bounds an ink storage space in the other end of the shell which is radially imperforate. Ink may flow from the storage space to the nib through an ink feeding channel between the weight and an inner shell wall. Threads on a first section of the outer, axial shell face permit the shell to be fastened in a tubular holder. A collar on the outer axial shell face is spaced intermediate the first face section and the nib center the shell in the holder. The collar defines a portion of an air channel axially by-passing the collar and communicating with the ambient atmosphere. A second axial portion of the outer face intermediate the threads and the other end of the shell defines a further portion of an air channel which communicates with the ink storage space.

What is claimed is: 
     
       1. Writing point assembly for a tubular drafting pen comprising: (a) an elongated tubular shell having a longitudinal axis;   (b) a tubular, capillary nib projecting in the axial direction of said shell from one terminal portion of said shell in the axial direction thereof, the other terminal portion of said shell being cup-shaped;   (c) a sliding weight guided in said shell and bounding an ink storage space in the axial direction in said other terminal portion, (1) said weight and an inner wall of said shell bounding a section of an ink feeding channel connecting said ink storage space with said nib;     (d) a tubular holder laterally enclosing at least an axially extending part of said shell;   (e) fastening means on a first section of the outer axial face of said shell for fastening the shell in said tubular holder;   (f) a collar on said outer axially extending face of said shell spaced intermediate said fastening means and said nib for centering said shell by engagement with said holder, (1) said collar defining a portion of an air channel axially by-passing said collar and said air channel communicating with the ambient atmosphere,     (g) a second axially extending section of said outer face intermediate said fastening means and said other terminal portion defining a further substantial portion of said air channel, said further portion communicating with said ink storage space over the cap-shaped other terminal portion of said shell; and   (h) two non-capillary annular grooves one located between said collar and said fastening means and the other located between said fastening means and said further substantial portion of said air channel.   
     
     
       2. An assembly as set forth in claim 1, wherein said other terminal portion has an outer face defining an axially extending passage and includes an apertured transverse wall bounding the bore of said shell, said further portion of said air channel communicating with said ink storage space through said passage and the aperture in said transverse wall. 
     
     
       3. An assembly as set forth in claim 1, said outer axial face being formed with two annular recesses, said recesses respectively separating said fastening means from said collar and said second axial section. 
     
     
       4. An assembly as set forth in claim 1, wherein said second axially extending section of said outer face includes a helical rib about said axis, said fastening means include threads on said first section, the pitch of said rib and of said threads being the same, the crest of said rib defining a cylindrical surface having a diameter substantially equal to the root diameter of said threads. 
     
     
       5. An assembly as set forth in claim 1, wherein said shell is free from radial perforations. 
     
     
       6. A tubular drafting pen as set forth in claim 1 comprising a writing point assembly secured in said tubular holder by said fastening means. 
     
     
       7. A pen as set forth in claim 6, wherein said other terminal portion has an axially extending face spaced opposite an inner axially extending face of said holder, said axially extending face of the other terminal portion and the inner axial face of said holder defining therebetween said further portion of said air channel. 
     
     
       8. A pen as set forth in claim 7, wherein said holder and said other terminal portion have respective radially extending end walls defining therebetween yet another portion of said air channel communicating with said further portion. 
     
     
       9. An assembly as set forth in claim 1, wherein (a) the air channel on the fastening means of the outer axial face of said shell and also in the further substantial portion rotates the said shell and follows a helical rib of the fastening thread by only 180 degrees axially by-passing the bounding helical rib and further rotating by 180 degrees in its extension continuing these steps each time until it ends in a further portion of said air channel defining said axial face of the outer terminal portion and the inner axial face of said holder and wherein (b) the major diameter of the shell of the substantial portion of the air channel corresponds to the minor diameter of the fastening internal thread of the holder covering the total axial extension of the substantial portion. 
     
     
       10. An assembly as set forth in claim 1, wherein the other cup-shaped terminal portion of the shell defines radial non-capilar slots by-passing the radially extending end wall thereof and partly the side walls of the said other terminal portion and the air channel communicating with said ink storage space.